A relict pronival (protalus) rampart in the Tararua Range, North Island, New Zealand

Brook, Martin S. and William, Jacob (2013) A relict pronival (protalus) rampart in the Tararua Range, North Island, New Zealand. Permafrost and Periglacial Processes, 24 1: 67-74. doi:10.1002/ppp.1759

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Author Brook, Martin S.
William, Jacob
Title A relict pronival (protalus) rampart in the Tararua Range, North Island, New Zealand
Journal name Permafrost and Periglacial Processes   Check publisher's open access policy
ISSN 1045-6740
Publication date 2013-01-01
Year available 2012
Sub-type Article (original research)
DOI 10.1002/ppp.1759
Open Access Status File (Author Post-print)
Volume 24
Issue 1
Start page 67
End page 74
Total pages 8
Place of publication West Sussex, United Kingdom
Publisher John Wiley & Sons
Language eng
Formatted abstract
Debris ridges in New Zealand are routinely assumed to be ‘moraines’ and used as key Southern Hemisphere paleoclimatic sites without detailed evaluation of ridge origin. Here we assess the origin of a debris ridge adjacent to Dundas Ridge in the Tararua Range, North Island, New Zealand, through measurements of ridge morphology and sedimentary properties. The ridge has a steep c. 35° distal slope (height 18 m), compared with the c. 19° proximal slope (height 6 m), and on all transects the distal slopes contain the coarsest material (median b-axis clast widths of 0.18-0.25 m), compared to distal samples (0.34-0.37 m). Clast shape (C40 range 40-60%) and angularity (RA>65%) indicate typically angular and ‘slabby’ clasts, and along with the lack of fines, and the ca. 40-m-distance between the ridge crest and the foot of the backwall, lead us to reject a glacial (moraine) origin for the ridge. The single ridge morphology precludes a protalus rock glacier origin, while the lack of a broad hillslope scar and debris apron beyond the ridge excludes a landslide origin. Instead, we interpret the ridge as a pronival (protalus) rampart formed by supranival debris supply–from the ca. 200 m-high southeastern slopes of Dundas Ridge–across a snowbed. Re-distribution of snow by prevailing westerlies from Mt Dundas Ridge into the basin would have nourished the snowbed, which is likely to have formed during the interval 24-18 ka BP, when a minor alpine-style glaciation affected sectors of the Tararua Range. This is the first pronival rampart detailed in New Zealand, raising the possibility that debris ridges of pronival origin may also be present elsewhere in New Zealand's mountains.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Geography, Planning and Environmental Management Publications
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Citation counts: TR Web of Science Citation Count  Cited 5 times in Thomson Reuters Web of Science Article | Citations
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Created: Fri, 11 Apr 2014, 01:26:50 EST by Claire Lam on behalf of School of Geography, Planning & Env Management